Parasitoid clutch size and irreversible evolution

Previously, theoretical and empirical studies suggested that parasitoids developing in small multiple‐egg broods would evolve siblicidal behaviour, making such brood sizes rare and single‐egg broods an evolutionary absorbing state. Recent evidence, however, suggests that small gregarious broods are relatively stable in many parasitoid taxa, and that gregarious development has evolved many times from solitary development. This suggests that new research is needed to assess how nonsiblicidal behaviour can spread and become stable. We discuss some potentially rewarding possibilities.